Would it be possible for you to attach the SLA, or a part of it that still exhibits the same behaviour? It's just that I'm not sure what you mean by an "invisible section".
It sounds like you might have gotten your layers "in a twist". Go to menu "Windows -> Layers" and check to see if you've got one that is printable (tick under the printer icon) but not visible (no tick under the eye icon).
Also, if something is "blanking out" text and not pictures it could be that you've got your text and images on different layers and something is getting between them. Check for unused/unwanted layers too.
You could also look at some of the text frames that "disappear" and see whether they're set as non-printable in the Properties palette (you'll see a printer icon with a white minus inside a red circle if they're set that way, just click the icon to toggle it back).